Acoustical ear muff and the like



Nov. 25, 1969 c. H. ALLEN 3,479,669

ACOUSTICAL EAR MUFF AND THE LIKE Filed Aug. 29, 1967 CLAYTON H. ALLEN, INVENTOR.

Mw /wALRi/vw ATTORNEYS United States Patent 3,479,669 ACOUSTICAL EAR MUFF AND THE LIKE Clayton H. Allen, Wellesley, Mass, assignor to Bolt Berauek and Newman Inc., Cambridge, Mass., a corporation of Massachusetts Filed Aug. 29, 1967, Ser. No. 664,154 Int. 'Cl. A42b 1/06 US. Cl. 2--209 5 Claims ABSTRACT OF THE DISCLOSURE This disclosure deals with a novel acoustical ear muff and the like emplyoing a novel friction-spring cushion that resists deformation except for a relative sliding movement between components thereof and that enables compliant application to the head or the like.

The present invention relates to acoustical ear muffler devices and, more particularly, to ear protectors that are employed to protect the hearing of the wearer against the damage of external noise.

While the art is replete with car muffs and earphones of'various types (all hereinafter generally referred to as ear muffs), there has previously not been a satisfactory solution to the problem of providing a sound-protecting ear muff or the like that has suflicient softness to permit ready and comfortable compliance with the head but that obviates the necessity for sizable pressure of the muff against the head, while adequately muflling both the low and high audible frequency sounds. While ear muffs have been provided with soft compliant cushions, the very softness of the cushion against the head inherently produces a yielding in response to low-frequency sounds that, in turn, vibrates the hard shell associated with the muff and creates sound pressure therewithin. This renders the wearer subject to the effects of low-frequency sounds. Attempts to overcome this problem have involved increasing the volume contained within the ear muff; but this forbids the use of such devices under helmets, or in other restricted applications. Other attempts to solve this problem have been to increase the pressure of the muff against the head; but this prevents the continual comfortable use of the muff over long periods of time. In addition, prior art muffs have employed relatively thick cushions which require a large central opening in order to admit the pinna of the ear. This construction, however, is diflicult to seal against the irregular contour of the head in the region surrounding the ear, and, in addition, leaves a relatively large unsupported central area that tends to allow pumping of air within the shell of the muff.

An object of the invention, accordingly, is to provide a new and improved ear muff that will not be subject to the difliculties above-mentioned. In accordance with the present invention, indeed, a new and improved ear muff has been provided which enables soft compliance with the head and at the same time provides minimal volume, minimal unsupported area, and minimal force against the head, while simultaneously overcoming the problem of mufiling the low frequency sounds (as well as the high frequency sounds) and, in addition, brings the pressure point of the muff very close to the ear and in intimate engagement with the head close to the base of the pinna of the ear.

Other and further objects will be explained hereinafter and are more particularly delineated in the appended claims.

In summary, the invention provides a friction-spring cushion device employing a resilient material which tends to determine the configuration of a first set of one or more rigid members constrained to slide with respect to a ice second set of one or more other rigid members and to provide, in combination, a configuration that is highly rigid against all directions of deformation except when sliding occurs between the two sets of rigid members.

The invention will now be described in connection with the accompanying drawing, the single featureof which is an isometric view, partially sectionalized to i1- lustrate details of construction.

Referring to the drawing, the ear muff of the invention is shown comprising an inverted cup-shaped shell 1, the peripheral flange 1 of which is received within an upper channel 2' of an elastomeric annular substantially frustoconical cushion or sealing member 2. A pressure ring 3 is interposed within the channel 2' to clamp the outer peripheral edge 1' of the hard shell 1 and pivotally clamp the outer peripheral edge 4 of a first set of rigid members 4 within the upper channel 2'. The first set of rigid members 4 is shown in the form of a resilient sheetmetal frusto-conical element having a plurality of radial slots 4" that define between them rigid resilient spring fingers 4". The fingers 4", as a result of this construction, are rigid in the radial direction along the length of the fingers, but provide a resilient force in the downward or vertical direction, in this figure. The lower or free ends of the fingers 4" are shown engaging a second set of rigid members, illustrated in the form of a pressure ring 6 received within a lower channel or lip 2" of the cushion 2 and preferably, though not essentially, in the form of a radially-corrugated resilient spring material providing a plurality of contact points for engagement with the free or lower ends of the fingers 4" of the first set of rigid members 4. The successive corrugation members in the element 6 serve to distribute the pressure radially over this annulus and to permit the conformance with the irregular surfaces of the head surrounding the ear in the circumferential or perimetrical direction as the lower rim portion 2" of the cushion 2 is applied to or pressed against the head. The dotted section to the left illustrates the original position, for example, of the left-hand portion of the muff before being pressed against a promentary point on the head.

In order to prevent motion of the resilient cushion 2 due to the influence of sound striking its external surface, the cushion material is preferably bonded, as at 8 to the member 4.

In accordance with this construction, accordingly, a light pressure against the ear muff will cause the lower cushion surface 2" to deform, urging the pressure ring 6 to force the fingers 4" to move inward (or upward in the figure) and at the same time to slide laterally along the surface of the pressure ring or plate 6 with a small Coulomb friction. This Coulomb friction is adjusted to be hardly noticeable in the process of deforming the cushion against the head in the normal manner of application. Once seated, however, any further deformation of the cushion involves the overcoming of the Coulomb friction force between the two sets of rigid members 4 and 6, and no deformation will take place until a force is applied sufiicient to overcome this Coulomb friction. Thus, the device is yieldingly highly rigid against de formation produced by small forces created by the influence of external sound pressures. Low auditory frequency sounds, therefore, that would cause yielding of the cushions of prior muffs and the resulting movement of the muff shell, thus do not produce such movement in accordance with the present invention. Otherwise stated, sound pressures which do not exceed the Coulomb friction and do not cause sliding between the members 4 and 6 leave the cushion substantially rigid and nondeformable. The cushion motion then is restricted to the motion permitted by the resilience of the flesh underneath the cushion between the cushion and the bone of the head. This yielding causes small changes in volume within the cushion-due to the unsupported area exposed within the enclosure. By thepresent invention, this area may be minimized by allowing the inner edge of the cushion qat 2" to closely approach the base of the pinna of: the ear; and, in fact, the inner edge may press against the head beneath the outer extremity of the pinna itself.

As an example of the performance of a cushion constructed in accordance with the invention and substantially. as illustrated in the drawing, the Coulomb friction force (that is the normal component thereof) may be adjusted to but a fraction of the normal 1 kilogram clamping force of present-day earphones and ear mutls. The wearer may, therefore, hardly detect the presence of this :Coulomb force. At least of the order of 10 db greater mufiling of'thelow audio-frequency sounds have thus been produced. with substantially the same high-frequency sound attenuation. 1, Clearly, other configurations of rigid members constit uting the above-referenced first and second sets may be employed including, for example, wire-loop configurations, hinged fingers with friction at the hinges, and other sliding spring configurations adapted to perform the functions above-described; and all such modifications are considered to fall within the spirit and scope of the invention as defined in the appended claims.

What is claimed is:

1. An acoustical ear muff and the like, having, in combination, resilient cushion means containing first and second rigid member sets engaged frictionally to slide laterally with respect to one another, but otherwise rigidly resistant to deformation, the cushion being yieldingly perimetrically deformable in response to forces in excess of the friction of said slide, but rigid against deformation produced by low-frequency external sounds and the like, the first set comprising a plurality of radially inwardly extending resilient fingers, the second set comprising a pressure ring engaging the said fingers, and in which said ring comprises a corrugated resilient annulus extending along the region of the cushion to be applied to the head. p

2. An acoustical ear muff and the like as claimed in claim 1 and in which the cushion comprises a substantially frusto-conical elastomeric cushion covered by a hard shell and carryingthe said engaged member sets.

3. An acoustical ear mud and the like as claimed in claim 2 and in which the said first member set is also of substantially frusto-conical configuration and the said ring extends along the region of the cushion to be applied to the head.

.4. An acoustical ear muff and the like as claimed in claim 1 and in which the said fingers are pivotally clamped at one end and slidingly engaged at the other member set at the other end.

5. An acoustical ear muff and the like as claimed in claim 4 and in which the cushion is bonded to said first member set.

References Cited UNITED STATES PATENTS 2,582,907 1/1952 Kaufmann 2209 2,593,892 4/1952 Kindel 2209 X 2,697,836 12/1954 Latiuca 2209 2,981,958 5/1961 Wadsworth 2209 HERBERT F. ROSS, Primary Examiner 

